The present invention relates to the field of computer networks, and in particular to a server specifically adapted to operate with a low-cost multi-media terminal.
Computer networks have been in existence for many years. The earliest networks were built using xe2x80x9cdumbxe2x80x9d terminals coupled to a powerful mainframe computer that serviced terminal users on a time-sharing basis. The xe2x80x9cdumbxe2x80x9d terminals consisted of little more than a keyboard, a monitor (such as a cathode ray tube or CRT), and a network interface. The capabilities of these terminals were limited to ASCII text and line-feed operation.
More recently, computer networks have been formed from combined platforms, e.g., workstation, personal computer (PC) and network computer (NC). These computer networks typically operate in a client/server framework in which many clients (operating on their platforms) connect to a single server or set of servers. The servers may provide client access to databases, the Internet, and application programs.
The most widely used computer network is the Internet. A client may select from several media sources for delivery of Internet access: a telephone company (telco) via a dial-up line, integrated services digital network (ISDN), digital subscriber line (DSL), cable access subscription, a dedicated Internet service provider (ISP) or some combination of these. A cable system using a fiber-optics line to the curb may enable transfer rates of 50 Mb/s, while the DSL switch features transfer rates between 1.5 Mb/s to 4 Mb/s.
A telco may provide each DSL subscriber a dedicated link to a central office, whereas a cable modulator/demodulator (modem) receives signals from a shared coaxial or hybrid fiber-coax cable system. Because of the shared nature of cable access, the cable transmission rate may diminish as the client load increases. Internet access for residential dwellings has been facilitated by the availability of cable service, whereas DSL has concentrated primarily on densely populated regions.
In contrast to the delivery of broadcast television service over a cable system, in which a low-cost audio/visual (A/V) decoder (such as a set-top-box) may be coupled to an analog receiver, Internet access over a cable system is largely associated with PC support hardware. A client may display images on a monitor using various standards such as video graphics array (VGA) or super VGA (SVGA). The accompanying module may be connected to the CPU. Also available to a client are memory storage/retrieval drives, a keyboard, a screen pointing device (most commonly a xe2x80x9cmousexe2x80x9d), a software operating system, and serial ports for sundry peripherals. This represents a sophisticated multi-media system. The PC enables a client to quickly provide specific instructions through an interactive menu such as a xe2x80x9cbrowser templatexe2x80x9d for Internet access, or the keyboard in a command-line window to edit a file formatted through an application.
A network computer is considered to be a xe2x80x9cthin clientxe2x80x9d, because the NC has less capability than a PC or workstation. A thin-client represents a user having only minimal hardware and corresponding software locally accessible for computer processing (such as a keyboard, monitor, and computer link). The thin client may log into a server with a username and password in order to attain access to the application programs and/or data files. A thin client may be considered a terminal dependent on the server to which it is connected for processing support, in contrast to a stand-alone self-contained PC. Except for the NC, a modern standalone platform supports a significant multimedia capability. Such a platform includes a sophisticated central processing unit (CPU), nonvolatile memory, supporting components and peripheral devices. These components contribute to the substantial cost of their respective platforms, not to mention the periodic upgrading of circuit-boards, peripheral drivers and application software. Although NC models may eventually achieve a sharply reduced purchase cost, these are comparatively sophisticated systems capable of executing sundry applications (such as Java applets).
Television reception and display represent technologies that predate the use of the PC and NC. Television equipment was designed for processing analog A/V signals. The A/V technology has been propelled towards digital media by the introduction of the digital video disk (DVD). Industry standards for compressing the A/V bitstream are defined by the Moving Photographic Expert Group (MPEG). The consumer electronics standard presently uses MPEG-2 that includes interlaced video and scalability. Interlaced video enables video frames to be divided into fields. Scalability allows coding for multiple bandwidth service. MPEG-2 uses lossy compression techniques to reduce memory storage requirements and intraframe coding to divide the frame into blocks and encode each block independently in a coder/decoder (codec). MPEG-2 video is established under International Standards Organization ISO/IEC 13818 Part 2, March, 1994.
The introduction of the WEBTV(trademark) network service, available from Microsoft Corporation of Redmond, Wash., has provided Internet access to the thin client through a server across telephone lines. Internet terminals for WebTV are produced by Sony Electronics, Inc. of Park Ridge, N.J. and Philips Consumer Electronics Co. of Eindhoven, Netherlands. These suppliers, along with Mitsubishi Consumer Electronics America of Irvine, Calif., manufacture Internet receivers for WebTV. However, while WebTV may enable a thin client to email a message and receive an Internet webpage, it does not support applications such as word-processing (much less multi-tasking of application programs), nor video encoding for image frame manipulation.
Application service providers (ASPs) have also begun marketing software applications that may be executed on a server at the behest of a user. An ASP delivers software applications and stores client data on its servers. While superfluous for a user having a state-of-the-art PC with adequate memory storage, the ASP creates a distribution and support framework for network delivery of software and support files for a less capable PC. However, the ASP nonetheless requires the client platform, such as a NC, to have sufficient processing capability to run the software.
It would be desirable to have a distributed display terminal system that has real-time video display and audio with all the responses that a workstation, PC or NC would have, at low cost and minimal complexity. It would also be desirable to provide this distributed display terminal system with video scalability, hardware portability and function versatility that can augment future generation computer capabilities.
A server for providing personal computer (PC) functionality to a user at a multimedia terminal processes commands from the user. The server includes a source upgrade processor, a client software component for receiving a command signal from the user, a display updater for combining signals and a video encoder for sending a digital audio/visual (A/V) data-stream to a multimedia terminal. The server enables concurrent computer application processing for multiple simultaneous thin client users each having a multimedia terminal using a communication link to connect them to the server.